Multicenter, double-blind, randomized, vehicle-controlled evaluates the efficacy and safety of patidegib gel, 2% and 4% in comparison with vehicle in subjects at least 18 years of age that meet the diagnostic criteria for basal cell nevus syndrome (BCNS). Subjects will be randomized to receive patidegib gel 4%, patidegib gel 2%, or the vehicle gel for a 26 week treatment period.